<template>
  <div class="pagination">
    <button :disabled="pageNo === 1" @click="changePageNo(pageNo - 1)">
      上一页
    </button>
    <button v-show="startEnd.start !== 1" @click="changePageNo(1)">1</button>
    <span v-show="startEnd.start > 2">···</span>

    <!-- 连续分页 -->
    <button
      :class="{ active: pageNo === index + startEnd.start }"
      v-for="(n, index) in startEnd.end - startEnd.start + 1"
      :key="index"
      @click="changePageNo(index + startEnd.start)"
    >
      {{ index + startEnd.start }}
    </button>

    <span v-show="startEnd.end < totalPage - 1">···</span>
    <button
      @click="changePageNo(totalPage)"
      v-show="startEnd.end !== totalPage"
    >
      {{ totalPage }}
    </button>
    <button @click="changePageNo(pageNo + 1)" :disabled="pageNo === totalPage">
      下一页
    </button>

    <span>共 {{ total }} 条</span>
  </div>
</template>
  
  <script>
export default {
  name: "Pagination",
  props: {
    total: {
      //总数
      required: true,
    },
    pageSize: {
      //每页展示数量
      type: Number,
      required: true,
    },
    pageNo: {
      //当前页码
      type: Number,
      required: true,
    },
    continues: {
      //连续页数
      type: Number,
      default:5
    },
    changePageNo: {
      type: Function,
      required: true,
    },
  },
  computed: {
    totalPage() {
      return Math.ceil(this.total / this.pageSize);
    },
    //计算连续分页初始值和结束值
    startEnd() {
      let { pageNo, pageSize, continues, totalPage } = this;
      // 初识值
      let start = 0;
      //结束值
      let end = 0;
      if (continues > totalPage) {
        start = 1;
        end = totalPage;
      } else {
        //计算
        start = pageNo - (continues - 1) / 2;
        end = pageNo + (continues - 1) / 2;

        //计算 不正常情况 连续分页: 当 start  < 1 ;start = 1;  end = continues
        if (start < 1) {
          start = 1;
          end = continues;
        }

        // 计算 不正常情况 连续分页: 当 end  > totalPage ;start = totalPage - continues +1;  end = totalPage
        if (end > totalPage) {
          start = totalPage - continues + 1;
          end = totalPage;
        }
      }

      return {
        start,
        end,
      };
    },
  },
};
</script>
  
  <style lang="less" scoped>
.pagination {
  text-align: center;

  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: gray;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #c81623;
      color: #fff;
    }
  }

  span {
    display: inline-block;
    line-height: 28px;
    font-size: 14px;
    color: gray;
    vertical-align: middle;
  }
}
</style>